I wrote a blog comment regarding Commodore 64 emulation on my group’s blog, but WordPress ate it. So I will post the general information here instead (and mention the blog below so we get automatic pingback here).
To emulate the C64 use VICE if on Linux or one of the many other supported platforms (also supports Windows).
I used to use the CCS64 emulator when I still used Windows. That emulator worked great at the time, but it has been several years since I tested it.
There is lots of information and C64 software available on C64.COM.
If you go the emulation route to C64 gaming you should get a proper joystick, in the good old days we did not use joypads. I like the Competition PRO USB ones. They are copies of the old Competition PRO sticks, but have USB interface instead of the old interface used by the C64/Amiga.
www.viceteam.org – VICE
www.computerbrains.com/ccs64 – CCS64
www.c64.com/?type=1&id=138 – Direct link to the page about The Great Giana Sisters.
www.vesalia.de/e_competitionusb.htm – Competition PRO USB Joystick, here sold together with an Amiga software bundle for Windows.
intro2gamedesign3.wordpress.com/2009/02/11/classic-game-review-the-great-giana-sisters – The original blog post essay for my online course on game design